NEW YORK

U.S. investigators on Thursday are working to determine why a married couple committed a deadly mass shooting in California that killed 14 victims.

Syed Farook, 28, and Tashfeen Malik, 27, were killed in an exchange of fire with police Wednesday, several hours after the initial rampage at a holiday party in San Bernardino.

Wearing black masks and armed with assault rifles and handguns, the couple opened fire at the party at around 11 a.m. local time (0300GMT), authorities said. A witness said the attackers fired for about 30 seconds before calmly reloading and opening fire again.

The FBI is leading the investigation to determine any political motivations for the shooting but officials said an ongoing investigation at a home in the nearby city of Redlands may yield clues to the reasoning behind the massacre, which also injured 17 victims.

“It is possible,” said President Barack Obama, that the shooting “was terrorist-related”, but he stressed that a definitive motive has not yet been determined. “It’s also possible that this was workplace related,” Obama said after meeting with his national security team and Vice President Joe Biden. “We’re going to get to the bottom of this.” 

In his brief remarks at the White House, Obama took the opportunity to again to push for gun control legislation.

“As the investigation moves forward it is going to be important for all of us, including our legislatures, to see what we can do to make sure that when individuals decide they want to do somebody harm, we’re making it a little harder for them to do it,” he said.  “Right now it’s just too easy."

The killings marked the deadliest mass shooting in the U.S. since the Sandy Hook Elementary School massacre in Connecticut in 2012, in which 26 people were killed, including 20 children.

There have been at least 351 mass shootings in the U.S. since January, according to ShootingTracker.com, a website that tracks news reports on shooting incidents.

Colleagues with the San Bernardino County health department who attended the holiday party described Farook as a quiet, polite, devout Muslim who had visited Saudi Arabia and returned married with Malik, whom he met online.

Farook, a U.S. citizen, was an environmental health specialist with the county’s health department, which was hosting the banquet party at the Inland Regional Center where the attack took place, according to CNN.

“The Muslim community stands shoulder to shoulder with our fellow Americans in repudiating any twisted mindset that would claim to justify such sickening acts of violence,” said Hussam Ayloush, who directs the Los Angeles chapter the Council on American-Islamic Relations, a Muslim advocacy group.

He urged the public to not jump to conclusions about any possible motive for the shooting.

American flags at the White House and all federal buildings has been lowered to half-staff until Dec. 7 in memory of the victims.